Superoxide dismutase activity in the cochlea.

It was found that superoxide dismutase (SOD) exhibits a higher specific activity in a fraction of the cochlea that contains the organ of Corti than in most other neural tissues. SOD may comprise as much as 4.3% of the soluble protein in this fraction. Approximately 74% of this SOD is cyanide-inhibitable, indicating that it is the Cu/Zn isoenzyme usually found in the cytoplasm. SOD activity was also found in a fraction containing the stria vascularis. Two enzymes that regulate peroxide concentrations, catalase and glutathione peroxidase, were also prominent in both of these fractions.